app.js

async function send_to_stripe(billing_data) {
  console.log(billing_data)
  stripe.customers.create({
    email: billing_data['email']
  }).then(customer => {
    const res = client.query('UPDATE customers SET stripe_customer_id=$1 WHERE email=$2', [ customer.id, billing_data['email'] ])
    return stripe.customers.createSource(customer.id, {
      source: "" // <- What do I put here?
      object: "card",
      name: billing_data['first_name'] + billing_data['last_name'],
      number: billing_data['card_num'],
      exp_month: billing_data['card_month_exp'],
      exp_year: billing_data['card_month_year'],
      cvc: billing_data['card_cvv'],
      address_city: billing_data['city'],
      address_line1: billing_data['address'],
      address_state: billing_data['state'],
      address_zip: billing_data['zip']
    });
  });
}